A multimedia priority service refers to a priority service initiated by an official of a government department such as the departments of state security and emergency affairs using a public network, in which case it is required to support the service preferentially under certain specific occasions such as when a jam occurs at the core network (CN) side or radio side of the communication network.
As shown in FIG. 1, when a voice call with high priority reaches the network at the side of a called user, the called user accesses from an Evolved universal Terrestrial Radio Access Network (E-UTRAN) consisting of eNBs (evolved Node B); a Mobile Switching Center (MSC)/Visitor Location Register (VLR) (wherein MSC and VLR are commonly used simultaneously) receives the incoming call request and sends a Circuit Switched (CS) paging request message via an interface between the MSC/VLR and a Mobility Management Entity (MME); the MME receives the CS paging request message and performs call Circuit Switched Fallback. In this case, a User Equipment (UE) is connected to the MSC via a GSM (Global System for Mobile communications) EDGE (Enhanced Data Rates for GSM Evolution) Radio Access Network (GERAN) or a Universal Terrestrial Radio Access Network (UTRAN).
As shown in FIG. 2, an existing Circuit Switched Fallback flow primarily includes the following steps.
Step 201. A UE has a call and the UE is the called user, at this moment the UE is in an idle state and has no connection with a network. An MSC of a called network in which the UE is located receives an initial address message of an incoming call request. A calling party of the incoming call request is a user with high priority, wherein a priority indication is included in the incoming call request; an MSC/VLR receives the incoming request, starts paging the called user, and sends an MME a CS paging request including a priority indication according to stored information on relevance relation and the like.
Step 202. The MME receives the CS paging request message sent by the MSC/VLR, starts paging the UE, and sends an eNB a paging message including a priority indication.
Step 203. The eNB sends the UE a paging message.
Step 204. The UE receives the paging message and sends the MME an extended service request.
Step 205. The MME sends the eNB a UE context SETUP request including a CS Fall Back (CSFB) indication and a priority indication.
Step 206. The eNB sends the MME a UE context SETUP answer message.
Step 207. The eNB decides to use a redirection mechanism and initiates a radio connection release to instruct the UE to redirect the UE itself to 2G/3G to perform a circuit domain service.
Step 208. The UE initiates radio connection at a GERAN/UTRAN, at this moment, as the GERAN/UTRAN is in a jammed state and incapable of processing a user service request, the UE is thereby unable to access a circuit domain service, leading to failure of the call.
A similar situation occurs when the UE is in a connected state (namely, the UE has a connection with a network), as shown in FIG. 3, a CSFB flow primarily includes the following steps.
Step 301. A UE has a call and the UE is the called user, at this moment the UE is in a connected state and has an existing connection with a network. An MSC of a called network in which the UE is located receives an initial address message of an incoming call request. A calling party of the incoming call request is a user with high priority, wherein a priority indication is included in the incoming call request; an MSC/VLR receives the incoming request, starts paging the called user, and sends an MME a CS paging request including an priority indication according to stored information on relevance relation and the like.
Step 302. A connection exists between the UE and the MME, and the MME directly sends the UE a CS service notifying message.
Step 303. The UE receives the CS service notifying message and sends the MME an extended service request.
Step 304. The MME sends the eNB a UE context modifying request including a CSFB indication and a priority indication.
Step 305. The eNB sends the MME a UE context modifying answer message.
Step 306. The eNB decides to use a redirection mechanism and initiates a radio connection release to instruct the UE to redirect the UE itself to 2G/3G to perform a circuit domain service.
Step 307. The UE initiates radio connection at a GERAN/UTRAN, at this moment as the GERAN/UTRAN is in a jammed state and incapable of processing a user service request, the UE is thereby unable to access a circuit domain service, leading to failure of the call.
A circuit domain call with priority is not guaranteed to succeed in an existing art when a GERAN/UTRAN is overloaded due to the aforementioned situation.